1. Field of the Invention
The present invention relates to a reciprocating compressor, and particularly, to a reciprocating compressor in which a stator and a magnet are fixed to a cylinder and the cylinder is moved.
2. Description of the Background Art
In general, a reciprocating compressor is an apparatus for sucking, compressing and discharging a gas as a piston linearly reciprocates in a cylinder.
As shown in FIG. 1, a conventional reciprocating compressor includes: a casing 10 provided with a gas suction pipe 12 and a gas discharge pipe 14; a reciprocating motor 30 disposed inside the casing 10, for generating a driving force; a compression unit 40 for sucking, compressing and discharging a gas by the driving force of the reciprocating motor 30; a resonant spring unit 50 for providing a resonant motion to the reciprocating motion of the reciprocating motor 30; and a frame unit 20 for supporting the reciprocating motor 30, the compression unit 40 and the resonant spring unit 50.
As shown in FIG. 2, the reciprocating motor 30 includes: an outer stator 31 having a cylindrical shape as a plurality of lamination sheets 31a are radially laminated outside a winding coil 31b; an inner stator 32 disposed to maintain a certain air gap from an inner circumference of the outer stator 31, and having a cylindrical shape as a plurality of lamination sheets 32a are radially laminated; and a mover 33 disposed to maintain a certain distance (A) from an outer circumference of the inner stator 32 and linearly reciprocating.
The mover 33 includes: a magnet 33b disposed between the outer stator 31 and the inner stator 32; and a magnet frame 33a to which the magnet 33b is fixed.
The compression unit 40 includes: a cylinder 41 having an internal space; a piston 42 disposed inside the cylinder 41, connected to the mover 33 of the reciprocating motor 30 and linearly reciprocating to change a volume of a compression space (P) in the cylinder; a suction valve 43 mounted at a front side of the piston 42 (hereinafter, a side where a gas is sucked is referred to as a rear side, and a side where a gas is discharged is referred to as a front side.), and operated according to pressure of the compression space (P) thus to open or close a suction passage (F) of a gas; a discharge valve 44 installed at a front side of the cylinder 141, for opening or closing a discharge passage of a compressed gas; a valve spring 45 elastically supporting the discharge valve 44; and a discharge cover 46 receiving the discharge valve 44 and the valve spring 45, and connected to the gas discharge pipe 14.
The frame unit 20 includes: a first frame 21 mounted at front sides of the reciprocating motor 30 and the cylinder 41; a second frame 22 connected to the first frame 21, for supporting the outer stator 31 of the reciprocating motor 30 together with the first frame 21; and a third frame 23 connected to the second frame 22, for supporting the resonant spring unit 50 together with the second frame 22.
The resonant spring unit 50 includes: a spring sheet panel 51 disposed between the second frame 22 and the third frame 23 and connected to the mover 33 and the piston 42 thus to linearly reciprocate; a first spring 52 disposed between the second frame 22 and the spring sheet panel 51, compressed when the piston 42 moves frontward and extended when the piston 42 moves rearward; and a second spring 53 disposed between the third frame 23 and the spring sheet panel 51, extended when the piston 42 moves frontward and compressed when the piston 42 moves rearward.
As shown in FIG. 3, in the conventional compressor, when power is applied to the winding coil 31b of the outer stator 31, a flux is formed between the outer stator 31 and the inner stator 32, and the mover 33 linearly reciprocates in a direction of the flux. Accordingly, the piston 42 connected to the mover 33 changes a volume of the compression space (P). By such volume change of the compression space (P), a gas is sucked to, compressed in, and discharged from the compression space (P). At this time, the first and second springs 52 and 53 provide a resonant motion to the piston 42, thereby allowing the piston 42 to smoothly reciprocate. And, such a series of processes are repetitively performed.
However, the conventional reciprocating compressor having such a structure is disadvantageous in that its assembly processes are complicated because the mover 33 is disposed between the outer stator 31 and the inner stator 32 and the mover 33 is connected to the piston 42 and the spring sheet panel 51.
In addition, because the mover 33 should be provided with a magnet frame 33a for supporting the magnet 33b, the number of components is increased, which causes a cost increase.
Also, a certain distance (A) between the mover 33 and the inner stator 32 has to be maintained, but such a distance (A) causes loss of magnetic force between the outer stator 31 and the inner stator 32, thereby degrading efficiency of the reciprocating motor 30. And outer diameters of the mover 33 and the compressor become great because of the distance (A) between the mover 33 and the inner stator 32, thereby causing problems such as an increase in usage of magnets 33b. 